A polyvinyl chloride composition is widely used as the material of resin molded bodies for building materials, for example. The polyvinyl chloride composition may be processed at high temperatures, and is therefore required to have high thermal stability. The polyvinyl chloride composition also needs to have high thermal stability to provide thermal stability for molded bodies. Further, color tone is an important consideration for resin molded bodies used as building materials, and therefore, the polyvinyl chloride composition also needs to have coloration resistance.
To meet these demands, a thermal stabilizer is generally added to a polyvinyl chloride prior to melt molding, in order to improve various kinds of performance such as thermal stability and coloration resistance.
Conventionally, a thermal stabilizer containing a heavy metal such as lead, cadmium, or barium has been used as the thermal stabilizer. However, as such heavy metals have toxicity and give adverse effects on the environment, thermal stabilizers and resin molded products free from a metal with high toxicity such as lead have been proposed.
Patent Literature 1, for example, discloses a stabilized halogen-containing resin composition containing a halogen-containing resin, and a composite of acid clay and/or activated clay and a calcium hydroxide-based compound represented by the formula: Ca1−x−yM2+xAly(OH)2, where M2+ represents a bivalent metal such as Mg, Zn, or Cu; and x and y are 0≤x<0.4 and 0≤y<0.1, respectively.
In recent years, with an increasingly growing interest for environmental protection and preservation, there is an increasing demand for a thermal stabilizer and a resin molded body free from even a heavy metal lower in toxicity than lead, such as tin. On the other hand, Patent Literature 2, for example, discloses a stabilizer composition containing a nitrogen-containing organic cyclic compound.
Even with use of this stabilizer composition, however, molded products unfortunately tend to be colored, and thus, the addition of a large amount of an expensive pigment or titanium oxide is required to prevent coloration.
Further improvement in performance has been desired for such resin compositions for molding that include such a heavy metal-free thermal stabilizer, as well as molded bodies.